1. Field of the Invention
This application is based on the European Patent Application No. 97830655.3, the content of which is incorporated hereinto by reference.
The present invention relates to a mirror mount having faces provided with projections defining a supporting plane, a method of manufacture comprising the mounting of mirrors on said faces and connection of said mirror mount to a suitable electric motor to form a mirror rotor and a mirror rotor obtained by said method.
2. Discussion of Prior Art
Many devices exist which in order to function need to generate, divert and deflect light beams, particularly laser light beams and which perform scanning of surfaces with such light beams, for example, scanners, optical code readers, fax machines, laser printers, medical apparatus, laser type measuring instruments for the construction industry, uneven surface detection instruments, etc.
These devices use mirror rotors for diversion, deflection and/or generation of light beam scanning.
The known mirror rotors comprise a polyhedral mirror mount and an electric motor capable of causing said mirror mount to rotate at preselected speeds. More particularly, the polyhedral mount is provided with a preselected number of absolutely flat external faces on which mirrors capable of guiding the optical beams are mounted and with an internal cylindrical cavity for connecting the mount to the rotor of the electric motor.
Said known polyhedral mounts are made of aluminium and are manufactured by machining the aluminium blank by means of machine tools. The faces defined to receive the mirrors are rendered perfectly smooth and free from burrs and the internal cylindrical cavity for connection to the rotor of the electric motor must have a very accurate diameter in order to prevent movements.
The mirrors are in turn obtained by depositing various numbers of layers (usually from 10 to 20) of a suitable dielectric material, e.g. silicon oxide, titanium oxide, magnesium fluoride, etc., on ordinary glass plates.
Production of the mirror rotor using such a conventional polyhedral mount comprises the following steps:
application of a layer of a two-component adhesive, e.g. UHU PLUS on the rotor of the electric motor, PA1 insertion of the motor in the polyhedral mount taking care to slide said rotor of the motor inside the internal cylindrical cavity of the polyhedral mount up to a stop flange, PA1 waiting the necessary time (usually from 20 to 30 minutes) for the adhesive to rigidly connect the rotor of the motor to the polyhedral mount, PA1 application of the above-mentioned two-component adhesive to the external faces of said polyhedral mount, PA1 waiting approximately 15 minutes for the viscosity of said adhesive to increase, PA1 placing the mirrors on the external faces of said polyhedral mount, PA1 waiting the necessary time (usually from 90 to 150 minutes) for the adhesive to rigidly fix the mirrors to the external faces of said polyhedral mount, PA1 startup and running of the mirror rotor thus produced, in order to test alignment of the mirrors with a reference point placed a distance of approximately 500 mm away. PA1 production of the aluminium blank mount made from bar aluminium and subsequent finishing of the same on a machine tool are somewhat laborious and lead to a certain percentage of wastes; PA1 whilst drying, the adhesive is subject to shrinkage and therefore, during the step of fitting the mirrors on the faces of the polyhedral mount, a continuous supervision by an operator is necessary in order to gradually correct the position of the mirrors with a rubber pad and return the same to the correctly aligned position. The operator consequently has to carefully and continuously supervise each rotor throughout the complete drying step of the adhesive, which since it has to take place at ambient temperature, takes several hours (approximately 4). Execution of this step must therefore be entrusted to very expert operators and for a long period of time.
This conventional production method has various disadvantages: